Manufacture of metaldehyde



Patented Get. 117, 1922.

UNHTED STATES HEINRICH DANNEEL AND EMIL Laser-Inn,

amma, CANTON or vanars, AND BASEL, swrrznnnxrmzrrarswnnx LONZA, orEBLAND.

No Drawing. Application filed February 2 To all whom it may ooacem:

Be it known that we, HEINRICH DANNEEL, a citizen of the German Republic,and ,EMIL Liisorrn-R, a citizen of the Swiss Republic, both residents ofBasel, Switzerland, have invented new and useful Improvements in theManufacture of Metaldehyde, of which the following is a full, clear, andexact specification.

Metaldehyde prepared from acetaldehyde is liable to lose weight, theloss being more rapid in proportion as the temperature is higher; forexample, although the loss at, or about, 20 centrigrade is hardlynoticeable it becomes appreciable at temperatures above say 30centigrade.

We have found the said loss to be due to the presence of small traces ofthe matterv used as catalyzer for transforming acetaldehyde intometaldehyde, such traces being carried down by theprecipitatedmetaldehyde, more especially when the precipitation oc-- curs suddenly,particles of catalyzer beingv then enveloped by the crystals ofmetaldehyde, so that these particles cannot be separated from I themetaldehyde by ordinary Washing.

According to this invention the stability of metaldehyde at hightemperatures is improved'by rendering harmlessthe residual traces of thecatalyzer still retained therein.

This can be effected either by transforming the residual traces of thecatalyzer which are not removable by washing, into 95 substances devoidof catalytic action; or by preventing the catalyzer coming 'into, actionby removin the liquid (chiefly paraldehyde) adherlng to the metaldehyde,the action of the catalyzer being dependent upon 40 the possibility ofsolution. There are several ways of carrying out this invention,including the. diminution of the activity of the catalyzer by otheragents, acting chemically, or physically, such as catalyst poisons, the

addition of collodial substances and the like.

The catalyzer can, for example, be converted into a chemical compoundwhich is insoluble in paraldeliyde and also (as far as possible) inwater. For instance, if sulfuric 5o acid has been used as the catalyzer,it can be transformed into the insoluble barium sulfate by means ofbarium hydroxide, barium carbonate, or other barium salt. If hydro- 0FBASE-L, SWITZERLAND, ASSIGNORS T0 MANUFACTURE OF METALTJEHYDE.

1, 1922. Serial No. 538,341.

chloric acid has been the catalyzer, it may.

be converted by a silver salt into silver chloride, and so on. The sameresult can be obtained by transforming the sulfuric acid into a saltwhich, though it may be soluble, has no catalytic action.

The adherent paralydehyde can be in part removed by washing it out forexample by means of a solvent, in which the paraldehyde is soluble, andwhich is itself either readily volatile, or capable of being washed outbya volatile liquid. We instance acetaldehyde as an example althoughwashing with acetaldehyde does not effect the complete disappearance ofthe paraldehyde ;.but the entire removal of this latter ca-nbe effectedby placing the product in a vacuum at a moderate temperature, say forexample, one of from 20 to 25 Centigrade.

In order to make certain that the object is perfectly attained, both theaforesaid means may be employed, the catalyzer being transformed into achemical compound which does not act catalytically, and the adherentparaldehyde being eliminated also.

The results of the invention are illustrated by the followingexperiment.

Large pressed blocks of metaldehyde were kept together, for example, forseveral days in succession, at a constant temperature of 35 centigrade,the loss in weight being as:

certained by weighing:

The losses amounted to:

Block f metaldehyde prepared in the ordinary way, 2.6 g.

Block of metaldehyde Washed with acetaldehyde, 1.6 g.

Block of metaldehyde treated with baryta water, 0.6 g.

Block of metaldehyde warmed in vacuo, 0.12 g.

What we claim is 1. As a new article of manufacture the herein describedmetaldehyde having an improved stability'at high temperatures, the

residual traces of catalyzer remaining therein being rendered harmless.2. The herein described improvement in the manufacture of metaldehydeconsisting in transforming the traces of catalyzer con tained in themetaldehyde into a chemical compound which has no catalytic action.

3. The herein described improvement in eme? the manufacture lefmeteldehyde consisting In witnees whereof we have hereunto ineliminating the para-lydehyde still a'dhersigned ur names'thisllth dayef Februery, ing to the metaldehydei 1922, in the presence of twosubscribing Wit- 4z. The fherein dscribeil igipdrovement in messes. 1 5the menu acture 0 meta de e consistin' in eliminating the pemldehy estill adher ing to the metaldehyde and 1h transformin k the traces ofcatalyzer contained in the me- Witnesses: 1

, taldehyde into a chemical compound which Fmsm: Km'z,

IOhas no catalytic action. YAMAND Rim.

